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Volume 33, Issue 6
Displaying 1-9 of 9 articles from this issue
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Hisashi Suzuki, Hideaki Matsubara, Noritoshi Horie1986 Volume 33 Issue 6 Pages 281-285
Published: August 25, 1986
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSThe carbon absorption of tungsten filament in hot-filament method was mainly studied in relation to the amount of diamond deposition on WC-Co substrate. The newly.used tungsten filament absorbed the carbon in the mixed gas of CH4 plus H2 at the initial stage of deposition treatment, so that the incubation period for the deposition, which was varied according to the CH4 concentration in a mixed gas, appeared. It was suggested that pre-carburizing treatment of tungsten filament in a gas having higher CH4 content was effective in order to stably deposit the diamond. Diamond was deposited also by passing hydrogen gas only through the pre-carburized filament.View full abstractDownload PDF (4228K) -
Osamu Yamada, Yoshinari Miyamoto, Mitsue Koizumi1986 Volume 33 Issue 6 Pages 286-290
Published: August 25, 1986
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSThe self-propagating high-temperature synthesis (SHS) method can be used to fabricate numerous ceramics in a very short time by taking advantage of exothermic reaction. In case of SiC, the heat released from exothermic reaction is not sufficient to convert the mixed powders of Si and C into SiC completely in the actual non-adiabatic system. This disadvantage could be overcome by a new ignition process, which we call "direct passing method of electric current". By using this method, stoichiometric β-SiC could be obtained efficiently with low electric power. The obtained β-SiC powder was sintered by using highpressure hot-pressing without additives and the properties of the compact were examined. The relative density, Vickers microhardness and fracture toughness of the β-SiC compact at room temperature were 98.0-98.6%, 35-36 GN/m2 and 5.6 MN/m3/2, respectively.View full abstractDownload PDF (3020K) -
A New Sintering EquationYuzo Mori, Hidetugu Yagi, Isao Konda, Kazuto Yamauchi1986 Volume 33 Issue 6 Pages 291-295
Published: August 25, 1986
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSA new sintering equation is derived on the basis that the neck growth during sintering is caused by the transfer of atoms on the neck surface of material unlike a conventional idea which is the transfer of the inner part of material.
The atomic flow on the surface is expressed as J=NC (f1-f2), where J is the flow of atoms in a unit area and a unit time in the surface, N is a number of atoms per unit surface area, C is the concentrationof the vacancy in the surface, fl is the jumping frequency from the surface to the space, and f2 is the jumping frequency from the surface to the bulk. From the above equation, it is clear that the fifth power of the neck radius x is proportional to the sintering time t in the equation of the neck growth which is composed of the physical constants of solid surface, and it can be estimated that the neck growth changes even in sintering in various atmospheric gases.
The new equation substituting the physical constants of the material explains well the experimental data after Kuczynski numerically.View full abstractDownload PDF (318K) -
Influence of Atmospheric Gas on Neck GrowthYuzo Mori, Hidetugu Yagi, Isao Konda, Kazuto Yamauchi1986 Volume 33 Issue 6 Pages 296-301
Published: August 25, 1986
Released on J-STAGE: December 04, 2009
JOURNAL OPEN ACCESSThe influence of the atmospheric gas on neck growth is examined theoretically and experimentally, as one of the methods confirming the new sintering equation proposed in the previous paper.
The probability surmounting the formation energy of vacancy on the surface is calculated from the amount of momentum and energy transferred to the atoms on the solid surface from the gas molecules by the collision. The probability becomes higher with increasing the molecular weight of gas. In this result it is estimated that the rate of neck growth will change with the kinds of atmospheric gas.
In the experiments of sintering between the copper wires, the neck radius grows larger in the Ar gas than the He gas. This means that the neck growth is changed by the atmospheric gas, so that the new sintering equation is confirmed.View full abstractDownload PDF (1466K) -
Yasuhiko Hashimoto, Shinichiro Ohmori, Koichiro Kohyama1986 Volume 33 Issue 6 Pages 302-305
Published: August 25, 1986
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSReaction-sintering of Cu-Ti-B alloys was investigated by heating the mixed powder compacts prepared from copper powder, TiH2 or Cu-Ti alloy powder, and boron powder at temperatures higher than the melting point of Cu.
Cu-TiB2 two-phase alloys were obtained by sintering when the atomic ratio Ti: B in the green compacts was adjusted to 1 : 2 regardless the choice of raw powders.
In the case of sintering the powder compacts prepared by the use of coarse boron powder of about 150 μm in particle size, thin fiber type TiB2, and thin and long needle type TiB2 crystals were precipitated in the copper matrices at the respective sintering temperatures of 1373K and 1473K.View full abstractDownload PDF (5404K) -
Youn Chai Kim, Teruhisa Watanabe1986 Volume 33 Issue 6 Pages 306-310
Published: August 25, 1986
Released on J-STAGE: November 19, 2010
JOURNAL OPEN ACCESSPhenomena appearing during sintering processes of the iron-tin-copper compacts admixed with 2.5 wt% of prealloyed and mixed powders having a Sn/Cu ratio of 35/65 were investigated.
The results obtained are as follows;
1) When the Fe-(0.87 Sn-1.63 Cu) compact admixed with the prealloyed powder is heated, the prealloyed powder particles are melted at about 1010K (737°C), and the liquid penetrates into the iron powder skelton. With rising temperature up to about 1163K (890°C), a little amounts of tin and copper also diffuse from the liquid into the iron, so that the sintered compact expands slightly. Most of the liquid therefore, lies around the neck of the iron skelton. Moreover, the composition of the liquid is more copper-rich than the initial Sn/Cu ratio, because the diffusional coefficient of tin into iron is higher than that of copper. Consequently, the sintered compact has much higher strength than the iron compact even at a low sintering temperature of 1163K (890°C).
2) When the Fe-0.87 Sn-1.63 Cu compact admixed with tin-copper mixed powders is heated, the tin powder particles are melted at 505K (232°C), and the liquid begins to penetrate into the iron powder skelton above 673K (400°C). Most of the liquid reacts with copper powder particles existing separately in the skelton, and becomes a tin-copper alloy, which has the same composition as the prealloyed powder used in 1) before reaching 1023K (750°C), because the tin liquid reacts more easily with copper than iron. Consequently, the properties of sintered compact admixed with the mixed powders is similar to that of the prealloyed powder.View full abstractDownload PDF (1950K) -
Hideshi Miura, Masatomo Kamada1986 Volume 33 Issue 6 Pages 311-317
Published: August 25, 1986
Released on J-STAGE: December 04, 2009
JOURNAL OPEN ACCESSThe sintering process and the spheroidization of pores in the iron compacts having a small addition of sulfides such as ZnS or CaS and the gas sulfurizing treatment were investigated by means of photomicroscopic examination, DTA and EPMA. The mechanical properties of Fe-S compacts were also investigated and the correlation between the spherical pores and the properties was discussed.
Upon sintering at above the eutectic temperature, a liquid phase of Fe-S was formed by the eutectic reaction of the Fe matrix and the FeS film formed at the pore surface and concentrated at the corners of sharp edged pores and at the interfaces between Fe particles. And the pore shape became more rounder without showing a remarkable shrinkage, which seemed to be due to the enhancement of neck growth between Fe particles by the surface diffusion mechanism. Because of the persistent presence of liquid phases connecting the pores during sintering, these pores were prone to coalesce easily.
A small addition of sulfides to Fe compacts had little influence on tensile strength but decreased elongation. The reason for this could be attributed to the notch effect of the residual FeS found mainly at the edge of pores. The spheroidization of pores made the behaviour of ductile-brittle transition more distinctive and increased the impact strength at high temperatures.View full abstractDownload PDF (7565K) -
Kazuhiko Majima, Masahiro Kihara, Keiichiro Shoji1986 Volume 33 Issue 6 Pages 318-324
Published: August 25, 1986
Released on J-STAGE: December 04, 2009
JOURNAL OPEN ACCESSA study has been made on the static tensile properties for both the as sintered and the β-quenched (water-quenched after holding at 1173K for 1.8 ks) Ti-Co binary alloys.
The elongation of the as-sintered Ti-Co binary mixed powder compacts lowered with increasing amount of Co content, and it was recognized that the value of elongation for the specimen containing only 2 wt%Co was lower than 5%. This elongation was not improved by the β-quenching, and the river pattern was observed in the α-phase region for both the as-sintered and the β-quenched specimens.
The above mentioned brittleness of the α-phase was confirmed to be related to the enrichment of oxygen in the α-phase.View full abstractDownload PDF (5594K) -
Kazuhiko Majima, Masahiro Kihara, Keiichiro Shoji1986 Volume 33 Issue 6 Pages 325-329
Published: August 25, 1986
Released on J-STAGE: December 04, 2009
JOURNAL OPEN ACCESSThe effect of (α+β)-quenching (water-quenching from 993K after β-quenching) on the static tensile properties of sintered Ti-Co binary alloys was investigated in relation to the additional amount of Co.
The remarkable improvement of the static tensile properties of sintered Ti-Co binary alloys containing less than 5%Co was obtained by the (α+β)-quenching. For example, the tensile strength and the elongation of the (α+β)-quenched Ti-5%Co specimen were 1100 MPa and 10%, respectively. However, the (α+β)-quenched specimen containing more than 6%Co showed the abrupt decrement of elongation due to the precipitation of fine particles along grain boundaries.View full abstractDownload PDF (4517K)
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